Mem. 17, pp

Fac. Sci., Shimane Umv., 71-80 Dec. 20, 1983

Developlnent of Streptophyllopsis kuroshioensis

(SEGAWA) KAJIMURA (Phaeophyta,

Laminariaceae) in culture

MitsuO KAJIMURA

Manne Brologlcal Station Shimane Unrversity Kamo Sargo Oki-gun, 685 Japan

(Received September 3, 1983)

Results of the wnter's observations on the development of a deep-sea Laminariaceous alga

Streptophyllopsis kuroshioensis in culture are described herein. They fundamentally agree with

those of other investigators on species in this order except Chorda filum in which the spo-

rophyte has sterile hairs. The evidences that the development of gametophytes and young

sporophytes of the alga observed is considered to occure in nature during winter to early spring

are described herein

Key Index Words : cultural study ; Laminariaceous alga ; Streptophyllopsis kuroshioensis.

Introduction

Streptophyllopsis kuroshioensis was reported as a new genus and a new combina-

tion by the present writer from the Oki Islands in 1981 (KAJIMURA 1981). This alga

has been reported from deep-waters off lzu, Shizuoka Prefecture on the Pacific coast

1

1 O cm

Fig. I . Streptophyllopsis kuroshioensis.

Habit of a sterile specimen of the sporophyte (OS9884) collected from the depth of

40 m off Tsuma on June 2, 1 983 and preserved in formalin seawater for 80 days

Contribution No. 22 from Oki Marine Biological Station, Shimane University

72 Mitsuo KAJIMURA (SEGAWA 1948) where Kuroshio Warm Current is washing along and the Oki Islands in

the Japan Sea where Tsushima Warm Current which is a branch of Kuroshio Current

is washing along and has a significant effect upon the algal vegetations (KAJIMURA 1981)

This alga is externally differentiated into perennial holdfast, perennial prostrate

branch, annual blade and stipe (Fig. 1). Sporophyte fruits in late autumn, the spo-

rangial sori are formed on both surfaces of the blade and stipe, and rejuvenation of the

sporophyte occurs in winter to early spring (KAJIMURA 1981), No report has been

made on the development of the gametophytes and young sporophyte of this alga up

to date. The present writer is fortunate enough to report the results of his observations

on it herein this time.

Materials and methods

The materials used for this study were collected from the depth of 35 m off Tsudo,

the Oki Islands on December 18, 1981

Surfaces of the fertile pieces of the plant were cleaned with gauze to remove poten-

tial contaminants. The cleaned fertile pieces of the plant were kept out of water on a

glass plate in the dark room at about 15'C for three hours to dry the surface of the

sporangial sori. Then the fertile pieces of the plant were immersed in 160 x 40 mm

dish of filtered sterilized seawater at about 16'C which corresponds to the mean water

temperature at the depth of 50 m in the Oki Islands in December (NAGANUMA 1973)

in 600 Iux illumination under a cool-white-fluorescent lamp to release the zoospores

The cell suspension was allowed to stand in the same condition half an hour after ob-

servation of the release of the zoospores under microscope. About 2 ml of the zoospore

suspension were removed by a Pasteur-type capillary pipette from just below the

surface of water into 88 x 15 mm petri dish of filtered sterilized seawater. About 2 ml

of the diluted zoospore suspension were removed into another petri dish of the same

size and filtered sterilized seawater in the same manner. The same process was repeated

successively twice more. Then about 3 ml of the most diluted zoospore suspenslon

were removed from the petri dish into each of the four 15.8 x 11.8x4.5 cm cubic

plastic vessels where five clean sterile microscope slides were spaced on the bottom

Each vessel was covered with a glass lid and kept at 15-18'C in 600 Iux constant illu-

mination under a cool-white-fluorescent lamp in a constant temperature room. The

culture medium was regularly changed with intervals of one week.

Abbreviations Used in Frgures

a anthendium e. a empty antheridium i. o intercalary oogonium

o oogomum r rhizoid

sp t. o

y. spo z

Development of Streptophyllopsis kuroshioensis

spermatozoid

terminal oogonium

young sporophyte

zygote

73

Results and discussion

Discharged zoospores are pyriform about 5 Ilm, 3 //m in average length and

diameter respectively and have a single chromatophore and two lateral flagella of une-

qual length but lack stigma (Fig. 2, A). Discharged zoospores show considerable

variations in morphology but they can not be divided into two different groups in size

After a period of mortility ranging from a few minutes to a few hours, the zoospores

come to lose the fiagella and rest, assume a rounded form, and secrete a wall about

themselves. Germination begins shortly afterward and in culture which is one day old

many germlings have evident germ tubes, and the single chromatophore divides once

(Fig. 1, B-E). The gametophyte is dioecious, microscopic and multicellular filament

which ramifies irregularly. The germination of zoospore is belonging to so called

"mediate filamentous type" (INOH 1947), namely a germ tube develops on each germling

of unicellular stage and the most of the cytoplasm and chromatophores migrate into

the termmal portion of the germ tube and then the germ tube comes to be delimited by

a cross wall from the embryospore case in two days old culture (Fig. 2, F). At this

time the chromatophores undergo further division. During the following about 10

days, growth is more or less limited to enlargement though a few to some additional

cells may be formed, and then it is possible to distinguish between the female and the

male gametophytes, the female gametophytes being of a greater diameter than the male

(Fig. 3). The female gametophytes ramify more inftequently than the male and the

female plant cells have more chromatophores than the male. Most gametophytes of

both sexes fruit in 30 days and young sporophytes may already be present at this stage

(Fig. 5-7). The oogonia develop mostly from the terminal cells but infrequently from

the intercalary. When an intercalary cell is transformed into an oogonium it forms a

lateral extension which serves as the apical portion of the oogonium (Fig. 13, 17)

When mature the egg is extruded through a rupture that arises at the apex of the oogo-

nium (Fig. 7, 16-17). A small amount of cytoplasm sometimes remains in the oogo-

nium. The extruded egg forms an ellipsoidal naked protoplast at the mouth of the

oogonium, where it remains in position and will be fertilized (Fig. 7, 16-17). The

male gametophytes are slenderer than the female. The antheridia are formed in clusters

at the tips of the branches or as outgrowths from intercalary cells (Fig. 22). Mature

antheridia usually contain a single chromatophore. Each antheridium forms only one

spermatozoid. The spermatozoids are observed to have a single chromatophore but

no stigma

Fertilization of the egg was not observed but the first noticeable change which

74 Mitsuo KAJIMURA

presumably follows the process of fertilization is the formation of a wall about the

zygote (Fig. 7, 1 6). The zygote then elongates and ultimately divides transversely

(Fig. 8). The next few walls are also in a transverse plane (Fig. 9-10, 18). Longitu-

dinal walls then set in, starting at the terminal end, and as a result growth takes place

in two different planes, giving rise to a somewhat elongated monostromatic sporophyte

2

A

D

": ' $' elF I edF

B~ C

E

lO 1lm

B

15 1lm

~

･ ~~ ･-

"R t.'..

.........

~~' . .. .

~) R

4

~),

5

~ o ~

~;

B

sp ~

:~~1 ' ' ~) 30 I/m

B ~

i

e

os

o ~ e

o ea

A

1 5 /Im a

Frg. 2-5 . Streptophyllopsis kuroshioensis

2, Zoospore m motile condition (A), embryospores (B-C), gametophyte half a day old (D),

same I day old (E) and same 2 days old (F) ; 3 , A young female gametophyte I O days old (A),

a young male gametophyte I O days old (B) ; 4, Two sterile female gametophytes 20 days old ;

5, A sterile male gametophyte 20 days old (A), a mature male gametophyte 30 days old and a

discharged spermatozoid (B)

Development of Streptophyllopsis kuroshioensis 75

6

B

z

o

y. spo 7

O

e ~e~j

e e o

z

eo e

~~

oe qb

~~

O

O

A

60 Iam

,-J e

~~eee

oo

~* "~~

~ee9 ~~oo c ~~ ~; 'eeo'

o eOe e O ~! 30 /Im G~e~~~)

L.__' ~~le e

8

y. spo

g

~:~~~ ~i ~)~~ ~b

,

y. spo

1~1~!

~-

~ l 5 /Im

O

, ~;"

~E~ ~~

o

i:e:'::,･.~,":'*~

,:

15 1lm

Fig. 6~9. Streptophyllopsls kuroshroensls

6, Habit of a sterile female gametophyte 25 days old (A), and a mature female gametophyte

35 days old with a zygote and a young sporophyte, each attached to emptied oogonium (B) ;

7, Habit of a mature female gametophyte 30 days old, showing two eggs and a zygote,

each attached to an emptied oogonium respectively ; 8, Part of a mature female

gametophyte 30 days old, showing a 2-celled young sporophyte attached to an emptied

oogonium ; 9, Same, showing a 3-celled young sporophyte

76 Mrtsuo KAJIMURA

10

5

y. spo

11

y. spo

~

~~;

~i

O

~: ~~ 15 /Im

1

q)o

o o

D

~

~~~

/ / / ll / / /

/ 1 *~ **.

L~)~~~ 1 5 Iam

~; _~eS" '~!.~~' '----

ai~fe'e8 e

~d~0$

o

~

12

O

1 5 pm

r

e~)~~~

~

e~~

~$i~ ~_e..__

13

Z

~!

t. o t. o

1. O

r

60 p L__

z

60 /Inl

c__t

Fig. 10-13. Streptophyllopsis kuroshioensis

10, Part of a mature female gametophyte 30 days old, showing a 4-celled young sporo-

phyte; 1 1, Same 35 days old, showing 13-celled young sporophyte; 12, Same 40 days

old, showing a 34-celled young sporophyte with two rhizoids arising from its basal portion ;

1 3, A fully developed female gametophyte 45 days old, showing a further developed sporo-

phyte, four zygotes, intercalary and terminal emptied oogonia

14

~

80 /Im L_]

Development of Streptophyllopsis kuroshioensis

15

L_,

77

840 pm r L_I

Fig. 14-1 5. Streptophyllopsis kuroshioensis.

14, Further developed young sporophyte attached to an emptied oogonium, distromauc

below, with several rhizoids arising from basal portion ; 1 5, Further developed young

sporophyte 1 30 days old and polystromatic in the lower portton

(Fig. 11-13, 19-21). One to several unicellular and simple rhizoids are formed from

the basal part of the monostromatic young sporophyte. Devel6pment of rhizoid does

not always accord with the one of the sporophyte. The rhizoids frequently contain

several chromatophores but they seem to degenerate later, and the tip of the rhizoids

irregularly ramifys taking frequently shape of pseudodisc ' (Fig. ' 12). The young sporo-

phytes become distromatic at a comparatively early stage by periclinal division of the

cells which starts in the basal region. The sporophytes shown ih figures 13 and 14 are

distromatic in the lower portion

Streptophyllopsis kuroshioensis can be considered to .agre~; fundamentally with

the following 30 species of Laminariales investigated by other phycologists in the

development of the gametophytes and young sporophytes but not with Chorda fi lu m of

which sporophyte has sterile hairs (KYLlN 1918, KANDA 1938) : Agarum cribrosum

(KANDA 194lb), Alaria angusta (KANDA 1944), A, crassifolia (KANDA 1936), A.

fistulosa (KANDA 1944), A. praelonga (KANDA 1944), Arthrothamnus blfidus (KANDA

1936), Costaria costata (KANDA 1936), Ecklonia cava (KANDA 194la), E. maxima

(PAPENFUSS 1942), E. stolomfera (KANDA 194la, NoTOYA and ASUKE 1983), Eckloniop-

sis radicosa (KANDA 194la), Eisenia arborea (CLARE and HERBST 1938, HOLLENBERG

1939), E. bicyclis (KANDA 194la), Kjellmaniella crasslfolia (KANDA 1938), Laminaria

angustata (KANDA 194lb), L. cichorioides (KANDA 1938), L. digitata (KYLlN 1916),

L. pallida (PAPENFUSS 1942), L. sinclairii (MYERS 1925), L. subsimplex (KANDA 1944),

78 Mitsuo KAJIMURA

16

50 /Im

19

40 /am :

Hg. 1 6-19. Streptophyllopsis kuroshioensis

Photormcrographs. 1 6, Part of a mature female gametophyte, showing an egg and

a zygote; 17, Same, showing an egg attached to an emptied intercalary oogonium;

1 8, Same, showing a 4-celled young sporophyte ; 1 9, Same, showing a young sporophyte

with a long rhizoid

Development of Streptophyllopsis kuroshioensis 79

Frg. 20-22. Streptophyllopsis kuroshioensis

Photomicrographs. 20, Part of a mature female gametophyte with an attached young sporophyte ; 2 1 , Same, showing a further developed monostromatic young sporo-

phyte; 22, Part of a mature male gametophyte, showing several clusters of antheridia

L. taeniata (KANDA 1944), L. yendoana (KANDA 1938), L. yezoensis (KANDA 1938),

Macrocystis integrlfolia (COLE 1968), Nereocystis luetkeana (KEMP and COLE 1961),

Pelagophycus porra (HERBST and JOHNSTONE 1937), Postelsia palmaeformis (MYERS

1925), Streptophyllum spirale (KANDA 1944)., Undaria peterseniana (KANDA 194la),

U. pinnatlfida (KANDA 1936).

From the facts mentioned .above it is considered that the development of the

80 Mitsuo KAJIMURA gametophytes and young sporophytes occurs during winter to early spring in nature in

the Oki Islands. This alga is considered to be different from Ecklonia maxima in

the season of the development of the gametophytes and young sporophytes because of

the fact that it occurs during spring and summer in the latter (PAPENFUSS 1 942)

Ackuowledgement

The present writer wishes to acknowledge his great indebtedness to Professor

Emeritus Jun TOKIDA Of Hokkaido University, for his helpful suggestions and critical

reading of the manuscript

Ref erences

CLARE, T. S. and HERBST, C. C. 1938. The life history of Eisenia arborea. Am. J. Bot. 25 : 494~98

CoLE, K. 1 968. Gametophytic development and fertilization in Macrocystis integnfolia. Can. J

Bot. 46: 777-782, pls. 1-3.

HERBST, C. C. and JoHNSToNE, G. R. 1937. Life history of Pelagophycus porra. Bot. Gaz. 99

339-354.

HOLLENBERG, G. J. 1 939. Culture studies of marine algae. I. Eisenia arborea. Am. J. Bot. 26 : 3~41

INOH, S. 1 947. Embryology of marine algae. HokuryOkan, Tokyo

KAJIMURA, M. 1 981. Streptophyllopsis a new gentis of Laminariaceae, Phaeophyta, from Japan

Mem. Fac. Sci., Shimane Univ. 15 : 75-87

KANDA, T. 1 936. On the gametophytes of some Japanese species of Laminariales. Sci. Pap. Inst

Algol. Res., Fac. Scu. Hokkaido Imp. Univ. 1(2) : 221-260, pls. 46Ji:8

1 938. On the gametophytes of some Japanese species of Laminariales II. Ibid. 2(1)

87-1 11, pls. 17-18.

1 94la. On the gametophytes of some Japanese species of Laminariales 111. Ibid. 2(1)

ll5-193, pls. 37-39.

1 94lb. On the gametophytes of some Japanese species of Laminariales IV. Ibid. 2(2)

293-308, pl. 59.

1944. On the gametophytes of some Japanese species of Laminariales V. Ibid. 3(1)

121-154.

KEMP, L. and CoLE, K. 1 961. Chromosomal alternation of generations in Nereocystis luetkeana

(MERTENS) POSTELS and RurRECHT. Can. J. Bot. 39 : 1711-1724, pls. 1-2

KYLIN, H. 1916. Uber Generationswechsel ben Laminaria digitata. Svensk Bot. Tidsk. 10(3) : 551-561 .

1 918. Studien tiber die Entwicklungsgeschichte der Phaeophyceen Svensk Bot Tidsk

12(1): 1-64.

MYERS, M. E. 1 925. Contributions toward a knowledge of the life-histories of the Melanophyceae

Univ. Calif. Publ. Bot. 13(4) : 109-124, pls. 8-10.

NAGANUMA, M. 1 973. On the new distribution of the mean water temperature in the Japan Sea. Proc

28th Jap. Oc. Res. Meet.: 1-36.

NoTOYA, M, and ASUKE, M. 1 983. Influence of temperature on the zoospore germination of Ecklonia

stolomfera OKAMURA (Phaeophyta, Laminariales) in culture. Jap. J. Phycol. 31: 28-33

PAPENFUSS, G. F. 1 942. Studies of South African Phaeophyceae. I. Ecklonia maxima, Laminaria

pallida. Macrocystis pynfera. Am. J. Bot. 29 : 1 5-24.

SEGAWA, S. 1 948. A new Laminariaceous alga found in lau. J. Fac. Agr.,KyOshn Univ. 9(1): 59-63